Water-soluble conjugated polyelectrolytes (CPEs) display strong photoluminescence and rapid transport of a singlet exciton along the π-conjugated backbone. Significant attention has been focused on amplified quenching of the CPE fluorescence by ionic quenchers. Amplified quenching effects have been demonstrated with quenchers that operate by either electron transfer or energy transfer mechanisms. In some CPE-quencher systems, Stern-Volmer constants for amplified quenching can be as large as 108 M−1. This highly efficient quenching in CPE-quencher systems has been attributed to ion pairing between CPE chains and oppositely charged quenchers and a rapid intrachain transport of the exciton. The large quenching response displayed by CPEs has led to their application in highly sensitive fluorescence-based sensors for biological targets. Some assays also have utilized layer-by-layer (LbL) coated latex or silica nano- and micro-colloids in combination with quencher-tether-ligand (QTL) or lipid bilayer assemblies to fix CPEs to a surface.
Examples of polymer grafted colloids and surfaces have been reported which are fabricated by using surface initiated living polymerization reactions, such as atom transfer radical polymerization (ATRP) and nitroxide mediated radical polymerization (NMRP). Although conjugated polymer LbL coated silica particles and conjugated polymer silica composites are known, a general method for preparation of silica particles that are surface-grafted with a conjugated polymer is not available. Beinhoff et al., Langmuir 2006, 22, 2411-14 discloses the preparation of a polyfluorene-based conjugated polymer grafted surface based on a Ni(0)-mediated step-growth polymerization reaction. By this approach, a silica substrate is modified with a cross-linked polymethacrylate network containing an aryl halide group. The aryl halide units serve as grafting points for a polyfluorene produced by a Ni(0) mediated step-growth polymerization reaction.
A general method for the grafting of a CPE to a surface, would allow the development of applications to these polymeric systems. Fluorescence sensing is one example of an application that can use surface grafted CPEs. Another application for the grafted CPEs is that of biocidal active agents.